Convertir image jpeg en niveaux de gris

//Capture d'une image avec caméra du smartphone
void CcameraDlg::OnBnClickedButton3()
{
// Capture de l'image
SHCAMERACAPTURE shcc;
ZeroMemory(&shcc,sizeof(SHCAMERACAPTURE));
shcc.cbSize= sizeof(SHCAMERACAPTURE);
shcc.hwndOwner= m_hWnd;
shcc.pszInitialDir = TEXT("\\My Documents");
shcc.pszDefaultFileName = TEXT("test.jpg");
shcc.pszTitle = TEXT("Camera");
shcc.VideoTypes = CAMERACAPTURE_VIDEOTYPE_ALL;
// Résolution 2M (1600*960) 3M (2048*1232) 5M (2592*1552)
// Resolution L (640*384) par defaut
shcc.nResolutionWidth = IMG_WIDTH;
shcc.nResolutionHeight = IMG_HEIGHT;
shcc.nVideoTimeLimit = 1;
shcc.Mode = CAMERACAPTURE_MODE_STILL;
shcc.StillQuality = CAMERACAPTURE_STILLQUALITY_HIGH;
HRESULT H=SHCameraCapture(&shcc);

}

//Affichage de l'image capturée en mode normal
void CcameraDlg::OnBnClickedButton6()
{
CDC * pDC = GetDC();
HBITMAP Hbitmap=SHLoadImageFile(_T("\\My Documents\\test.jpg"));
if(Hbitmap)
{

CBitmap bitmap;
bitmap.Attach(Hbitmap);

BITMAP bmpInfo;
bitmap.GetBitmap(&bmpInfo);

CDC bitmapDC;
bitmapDC.CreateCompatibleDC(pDC);
bitmapDC.SelectObject(&bitmap);
CRect RC;
GetClientRect(&RC);
pDC->StretchBlt(0, 0, RC.Width(), RC.Height(), &bitmapDC,
0, 0, bmpInfo.bmWidth, bmpInfo.bmHeight, SRCCOPY);
bitmapDC.DeleteDC();
bitmap.DeleteObject();
}
}



//Conversion et affichage l'image en niveau de gris
void CcameraDlg::OnBnClickedButton1()
{

}